Rheumatoid arthritis (RA) patients and their healthcare providers frequently use the term ‘flare’ to describe periods of worsening disease activity. The term is not well defined and reflects a continuum of clinical experiences that is highly dependent on individual contextual factors.1,–,5 What constitutes a flare for one patient may not be the same as for another; what patients describe as a flare may be quite different from what a clinician considers significant; and the level at which symptoms become unmanageable may also vary from patient to patient and even in the same patient over time depending on disease activity, treatment effects and coping strategies. And while ‘flare’ is a commonly used term in English, it is not necessarily easily translated into other languages.2 With advances in RA treatment and improved outcomes, a careful study of the manifestations of flare is needed to identify patient-relevant elements that may encompass features beyond our current core set of outcome measures.

Early intensive treatment strategies that include combinations of non-biological and biological disease-modifying antirheumatic drugs are used to reach a treatment goal of remission or a very low disease activity state.6,–,10 By moving more patients to states of low disease activity, we now face new questions in clinical practice, namely how to taper therapy to maintain efficacy, to improve longer-term safety and potentially to lower costs. There is a limited evidence base from clinical practice and clinical trials to guide such decisions, partly because there is no standardised measure to assess significant disease worsening, or flare. By convention, an inversion of improvement criteria (driven predominantly by physician-assessed variables) has often been adopted,11 12 with an assumption that the magnitude of relevant change for worsening and improvement will be similar, although studies suggest …